1. Field of the Invention
The present invention relates to an image forming apparatus such as an electrophotographic printer, more particularly to its control system.
2. Description of the Related Art
An image forming apparatus may have a plurality of containers storing paper or other printing media to which images can be transferred. When a host device to which the image forming apparatus is connected sends image data, the host device also sends a command selecting one of the containers, and the apparatus feeds printing media from the selected container. (One example of such an apparatus is described in Japanese Utility Model Application Publication No. H9-368.)
If one of the containers is empty, the apparatus typically displays a notification message, and goes offline until the supply of printing media in the empty container is replenished. Although the user of the host device might prefer to select a different container and carry out image-forming operations with media from that container, this desire is frustrated by the refusal of the image forming apparatus to accept further commands from the host device while in the offline state. The user must either replenish the printing media or wait for someone else to do so.
(The apparatus described in Japanese Utility Model Application Publication No. H9-368 automatically selects a container containing printing media, but this is also problematic, as the apparatus may select a container with printing media on which the user does not wish to form an image.)
Similar inconveniences occur during factory tests and inspections of the image forming apparatus, and during maintenance in the field. Further information will be given in the detailed description of the invention.